The present invention relates to a portable electronic calculator having incorporated therein a writing instrument such as, for example, a ball-point pen, that is, a calculator which can be used both as a writing instrument and as a portable electronic calculator.
Recently, thin, card-type portable electronic calculators have been placed on the market. These calculators are handy to carry but mechanically weak because of their small thicknesses. A portable electronic calculator of the type having a writing instrument is very convenient since it is possible to write down the result of a calculation without using another writing instrument, or to conduct further calculations immediately after writing down the result of a previous calculation; namely, there is no need of carrying a calculator and a writing instrument separately.
In view of the above, there have been proposed portable electronic calculators in U.S. Pat. Nos. 4,029,915 issued June 14, 1977 and 4,128,889 issued Dec. 5, 1978. In the calculator of the former patent, keys are arranged in a row but four inputs are selectively entered by one key, so that it is likely to erroneously operate the keys. The calculator of the latter patent is almost free from the erroneous key operation in that one input is entered by one key, but since the keys are arranged in three rows on a cylindrical body, the keyboard is not flat but forms a part of the cylindrical surface of the body and, consequently the keys are somewhat difficult to operate. In either case, since the keys are exposed on the surface of the body, they act as a hindrance when the calculator is inserted into or taken out of a pocket. Further, since a ball-point pen is housed at the center of the cylindrical body, if the length of the body is limited, the ball-point pen must be reduced in length because of relative arrangements of various parts.
A writing instrument is generally made long and slender so that it easy to use, and a portable electronic calculator having a flat control panel is easy to operate. Accordingly, it is advantageous to combine a calculator of a rectangular, elongated configuration with a writing instrument. In this case, however, if the calculator body is made too thin, it is readily broken and, even if not broken, it is bent and difficult to use as the writing instrument.
It is an object of the present invention to provide a portable electronic calculator with a writing instrument which has a thin, elongated configuration and is neither broken nor deformed when the writing instrument is used and which allows ease in the use of the writing instrument and in the operation of the calculator.
Another object of the present invention is to provide a portable electronic calculator with a writing instrument which can easily be inserted into or taken out of a pocket.
Another object of the present invention is to provide a portable electronic calculator with a writing instrument which permits easy replacement of the writing instrument.
Yet another object of the present invention is to provide a portable electronic calculator which is easy to assemble.